Assessment of retinal sensitivity function in response to intravitreal injection therapy for diabetic macular edema (DME)

The prevalence of center-involving or referral diabetic macular edema (CI-DME) and non -center involving diabetic macular edema (NCI-DME) in the south urban population was 2.4 to 3.03% and 8.9 to 10.80% [1, 2] The overall prevalence for DME with tele-screening was 3.9% (95% CI: 3.7–4.1)[3]Monthly intravitreal injections of Bevacizumab for up to 6 months were administered for ischemic DME patients which improved best corrected visual acuity (BCVA) (20/180 to 20/74) and macular sensitivity (11.66 to 16.26 dB) without perfusion compromise in the macula. Capillary dropout areas in optical coherence tomography angiography (OCTA) correlated with lower retinal sensitivity in microperimetry. [4] Several types of anti-vascular endothelial growth factor’s (VEGF’s) are available for treatment in DME cases that include: bevacizumab, ranibizumab, aflibercept and conbercept. Among these aflibercept and conbercept have shown efficacy and safety in clinical trials. [5] Two years of a study conducted on DME showed no difference in visual outcomes, injection no and reduction of central macular thickness by bevacizumab, ranibizumab and aflibercept.[6] However, use of corticosteroid treatments such as triamcinolone, dexamethasone and fluocinolone acetonide can elevate intraocular pressure and cataract progression.[7] Thus the choice of therapy should be varied on case basis with the use of intravitreal anti-VEGFs on DME.[8] Anti-VEGFs also predicts the mean increase in logarithm of minimum angle of resolution (logMAR) in visual acuity during third and sixth months. There is also significant increase in macular sensitivity with decreased mean macular thickness.[9]OCTA evaluates DME with larger baseline foveal avascular zone areas (FAZ) in deep vascular plexus to have worsening visual acuity outcomes and higher decrease in superficial vascular plexus vessel density were associated with worsening of retinal sensitivity over one year.[10] These investigations can support OCTA the early detection and monitoring of diabetic macular ischemia rather than using fluorescein angiography (FA) which does not confirm the worsening of macular perfusion post-anti-VEGF treatment. [11] Also, OCTA studies have demonstrated the use of non-comparative case series during anti-VEGF treatment. This can create norms to identify diabetic macular ischemia (DMI) phenotypes during therapeutic interventions. These can be identified by using vascular and neuronal parameters to explain the recurrence of diabetic macular edema.[12] Mean retinal sensitivities within central 2° and 10° are lower in DME as compared to non-DME patients.[13] It will be interesting to see these sensitivity changes across different sectors with other alternative anti-VEGFs that can confirm the changes in macular ischemia. This study examines the evaluation of OCTA metrics for structure and microperimetry for retinal sensitivity changes among pre and post-administration of anti-VEGF injections in patients with  diabetic macular edema.